Embodiments of the invention relate generally to electric drive systems including hybrid and electric vehicles and, more particularly, to rapidly charging one electric drive system using shared power electronics of one or more additional electric drive systems.
Hybrid electric vehicles may combine an internal combustion engine and an electric motor powered by an energy storage device, such as a traction battery, to propel the vehicle. Such a combination may increase overall fuel efficiency by enabling the combustion engine and the electric motor to each operate in respective ranges of increased efficiency. Electric motors, for example, may be efficient at accelerating from a standing start, while combustion engines may be efficient during sustained periods of constant engine operation, such as in highway driving. Having an electric motor to boost initial acceleration allows combustion engines in hybrid vehicles to be smaller and more fuel efficient.
Purely electric vehicles use stored electrical energy to power an electric motor, which propels the vehicle and may also operate auxiliary drives. Purely electric vehicles may use one or more sources of stored electrical energy. For example, a first source of stored electrical energy may be used to provide longer-lasting energy while a second source of stored electrical energy may be used to provide higher-power energy for, for example, acceleration.
Plug-in electric vehicles, whether of the hybrid electric type or of the purely electric type, are configured to use electrical energy from an external source to recharge the traction battery. Such vehicles may include on-road and off-road vehicles, golf cars, neighborhood electric vehicles, forklifts, and utility trucks as examples. These vehicles may use either off-board stationary battery chargers, on-board battery chargers, or a combination of off-board stationary battery chargers and on-board battery chargers to transfer electrical energy from a utility grid or renewable energy source to the vehicle's on-board traction battery. Plug-in vehicles may include circuitry and connections to facilitate the recharging of the traction battery from the utility grid or other external source, for example. The battery charging circuitry, however, may include dedicated components such as boost converters, high-frequency filters, choppers, inductors, and other electrical components dedicated only to transferring energy between the on-board electrical storage device and the external source. These additional dedicated components add extra cost and weight to the vehicle.
In addition, the total current available for recharging the on-board electrical storage device using only the on-board battery charging circuitry of the vehicle is limited to the total current that the on-board battery charging circuitry can supply. The on-board electrical storage device, however, may be designed to accept a charging current much greater than the total current supplied by the on-board battery charging circuitry. Increasing the total current supplied by the on-board battery charging circuitry typically includes increasing the size and capacity of the circuitry components, which adds yet additional cost and weight to the vehicle.
It would therefore be desirable to provide an apparatus to facilitate the transfer of electrical energy from multiple external sources to the on-board electrical storage device of a plug-in vehicle that reduces the number of components dedicated only to transferring energy between the on-board electrical storage device and the external source and that increases the total current available for charging the on-board electrical storage device.